Dissemination of wear particles to the liver, spleen, and abdominal lymph nodes of patients with hip or knee replacement

Spinal implant wear particles: Generation, characterization, biological impacts, and future considerations

The generation of wear debris from orthopedic implants is a known cause of implant failure, particularly in joint replacements. While much research has focused on wear particles from knee and hip implants, spinal implants, such as total disc replacements (TDRs), have received less attention despite their increasing clinical use. Spinal implants face unique biomechanical challenges, including a wider range of motion and higher loads, leading to complex tissue interactions. Studies reveal that TDR wear particles, though similar in size to those from knee implants, cause a stronger immune response, with more macrophages and giant cells found in the surrounding tissue. This may explain the high revision rates seen in spinal surgeries, with some interventions failing in over 30% of cases within 10 years. The younger population undergoing spinal surgery, combined with the productivity losses associated with implant failure, underscores the need for greater understanding. This review discusses recent research on the generation, characterization, and biological impacts of spinal implant wear debris. It draws on retrieval analysis, wear simulation, in vivo models, and a survey conducted with the AO Spine Knowledge Forum Degenerative to assess current clinical practices and highlight gaps in knowledge. Additionally, this critical review explores future strategies to reduce the biological impact of wear particles and improve the safety and longevity of spinal implants through better therapeutics and design innovations. By combining literature and clinical insights, this paper aims to guide future research in addressing the complexities of spinal implant wear and its biological consequences.

Can Lymphatic Transport Impaired by Total Knee Arthroplasty be Managed with Manual Lymphatic Drainage?

Objective: It is known that particles released from the prosthesis due to wear after joint replacement surgery affect the lymphatic system. This study aimed to investigate the effect of the manual lymphatic drainage (MLD) technique on pain, edema, and blood lactate dehydrogenase (LDH) levels in the early period of lymphatic transport affected by total knee arthroplasty (TKA). Method: Twenty-four patients who underwent TKA were randomly allocated (control: 12; MLD: 12). Both groups received postoperative rehabilitation. The MLD group also received MLD in the first 3 days after surgery. Clinical assessment was undertaken on the third day and at the sixth week postoperatively. The Visual Analog Scale (VAS) was used for pain during activity, algometer measurements for pain threshold levels, and the Frustum method for leg volumes. The LDH was recorded using laboratory measurements. Results: A significant difference was found in the VAS activity-related pain scores of the groups according to the assessment time (MLD: χ2 = 47.175; p = 0.000; control; χ2 = 30.995; p < 0.000). The pain threshold significantly increased in the MLD group from postoperative day 2 (2nd day, 3rd day, 6th week, respectively; p = 0.015; p = 0.001; p < 0.000). Leg volume significantly decreased over time in both groups after surgery (p < 0.001); however, there was no significant difference between the groups (first-third postoperative days and sixth week; p = 0.192; p = 0.343; p = 0.453; p = 0.908, respectively). While the LDH significantly decreased after drainage in the MLD group (first-third postoperative days; p = 0.002; p = 0.005; p = 0.006, respectively), it increased with exercise in the control group, first day (p = 0.004) and second day (p = 0.019). Conclusions: MLD added to exercise therapy is more effective than exercise therapy alone in reducing the LDH level, a marker of pain and muscle damage, but is not effective for edema due to surgery.

Cobalt-Chromium-Molybdenum Femoral Knee Implant Damage Correlates With Elevated Periprosthetic Metal Concentrations

BACKGROUND

Total knee arthroplasty (TKA) device systems frequently include cast cobalt chrome alloy (CoCrMo) femoral components. However, compared to total hip arthroplasty (THA), gaps persist in our understanding of the correlations between femoral component damage, local metal release, and potential biological effects. Additionally, it remains unclear how TKA metal release affects clinical success or patient satisfaction. In this study, we investigated the associations between implant damage and metal release in the periprosthetic tissues following TKA. We asked: (1) does damage severity correlate with increased metal concentrations within the periprosthetic tissue? and (2) does the magnitude of metal released from CoCrMo femoral components merit clinical concern?

METHODS

There were 51 CoCrMo femoral components and synovial samples that were prospectively collected by an institutional review board-exempt retrieval program. Devices received damage scores ranging from minimal (1) to severe (4). Tissue metal concentrations for cobalt (Co), chromium (Cr), molybdenum (Mo), and titanium (Ti) were quantified using inductively coupled plasma mass spectroscopy.

RESULTS

Visual damage correlated with increases in Co, Cr, and Mo concentrations in the periprosthetic tissue (P = 0.0008, 0.029, and 0.007, respectively). Within the tissue adjacent to severely damaged implants, we measured median Co, Cr, and Mo concentrations of 7.81, 5.26, and 0.713 μg/mL, respectively. For minimally damaged implants, we report median Co, Cr, and Mo concentrations of 0.111, 1.80, and 0.179 μg/mL, respectively. In several of the 51 (14%) tissue samples, we measured Co and Cr concentrations > 10 μg/mL. Additionally, within periprosthetic tissues of devices with Ti tibial trays, Ti concentrations increased (P = 0.0052) arising, in part, from tibial-femoral component contact during arthroplasty.

CONCLUSIONS

We (1) showed elevated periprosthetic tissue metal concentrations in TKA patients and (2) established a positive correlation between damage severity and subsequent metal release. Measured tissue metal concentrations approached the magnitudes reported following metal-on-metal THA.

Target Organs of Metals Released from Metal-on-Polyethylene Knee and Hip Arthroplasty Implants: Implications for Tissue Metal Profiles

Metals are used in orthopedic implants. The wear of arthroplasty implant can lead to the release of arthroprosthetic metals, both locally and systemically, after migration into the organs. While the toxicity of metal-on-metal arthroplasty implants is well-known and monitored, the toxicity associated with metal-on-polyethylene (MoP) ones is not as comprehensively understood. This study aimed to investigate the release of metals from MoP arthroplasty implants and their impact on the tissue metal profile in autopsied individuals, comparing them to deceased controls without prostheses. High-resolution ICP-MS was employed to analyze 39 metals in the blood, urine, hair, organs, and periprosthetic tissue of 25 deceased individuals with arthroplasty implants and 20 control subjects (Prometox study, protocol ID: APHP180539, NCT03812627). Eight metals (beryllium, chromium, cobalt, lanthanum, molybdenum, nickel, tellurium, titanium) exhibited significant impacts in arthroplasty implant wearers across various organs. Increased concentrations of La and Be were observed, the origin of which could not be precisely defined within the scope of this study. Notably, the lungs emerged as the primary target organ for metallic ions contained in implants. This study suggests that MoP arthroplasty implants, even when functional and not visibly worn, release arthroprosthetic metals into the body, potentially causing disturbances. Furthermore, considering the presence of an arthroplasty implant in autopsy reports may be relevant, as the released metals could influence the tissue metal profile.

Microwave-Sintered Nano-SiC Reinforced 8SiC/Ti-3Cu Composite: Fabrication, Wear Resistance, Antibacterial Function, and Biocompatibility

The significance of biomedical applications of Ti alloys is best emphasized by their widespread utilization as implantable materials, such as internal supports and bone replacements. Ti alloys are sensitive to fretting wear, which leads to the early failure of Ti implants. Improved wear resistance of such implants is essential to ensure a prolonged implant life. Based on the structure-function-integrated concept, this work unprecedentedly designs and fabricates an antibacterial 8SiC/Ti-3Cu composite with improved wear resistance using microwave sintering from pure Ti, Cu, and nano-SiC powders. For comparison, SiC-free Ti-3Cu composite is manufactured under the same conditions using microwave sintering. The addition of 8 vol.% SiC to Ti-3Cu significantly reduces the porosity and pore size of composites. The 8SiC/Ti-3Cu shows a Vickers hardness of 353 HV, compressive strength of 803 MPa, elastic modulus of 28.7 GPa, and a significantly increased wear resistance (wear rate decreased by 70% compared to Ti-3Cu). In addition, 8SiC/Ti-3Cu exhibits excellent electrochemical corrosion resistance, biocompatibility in relation to MC3T3-E1 cells, and a bacteriostatic rate over 99% against E. coli. The combination of the wear-resistant nano-reinforced SiC and antibacterial Ti2Cu in the 8SiC/Ti-3Cu composite renders it a highly promising implant material.

Investigating the inflammatory effect of microplastics in cigarette butts on peripheral blood mononuclear cells

Cigarette filter microplastics are composed of cellulose acetate that does not undergo biological or photo-degradation. These microplastics are readily dispersed and can be found abundantly in water, soil, and air. These fibers possess high absorption capabilities, allowing them to collect and retain pollutants such as toxic elements. As a result, they are regarded as potential dangers to living organisms. The purpose of this study was to analyze the immune response of human peripheral blood mononuclear cells (PBMCs) when exposed to cigarette filter microfibers, measuring the secretion of the inflammatory cytokines TNFα (tumor necrosis factor-alpha) and IL-6 (interleukin-6). In this study, we examined how used cigarette cellulose acetate microfibers affect the viability of peripheral blood mononuclear cells in an appropriate culture medium at three concentrations: 50, 100, and 200 µg/ml. In addition, this study investigated the release of inflammatory cytokines TNFα and IL6 from PBMCs exposed to 200 µg/ml cigarette filter cellulose acetate. The results showed that increasing the concentration of cellulose acetate fibers of one of the brands in the culture medium has a significant effect on reducing cell viability. The 200 µg/ml in DW is more effective than 50 and 100 µg/ml in reducing cell viability. Peripheral blood mononuclear cells showed an inflammatory immune response when exposed to 200 µg/ml cellulose acetate from cigarette filters. They produced inflammatory cytokines that showed a significant increase compared to the control sample. In general, it can be concluded that cellulose acetate fibers in contact with body cells stimulate them and cause an inflammatory response.

How In Vivo Alteration of Hip Replacement Wear Mode Can Cause a Voluminous Inflammatory Reaction and an Excessive Titanium Exposure

Background: Wear particle reaction is present in every arthroplasty. Sometimes, this reaction may lead to formation of large pseudotumors. As illustrated in this case, the volume of the reaction may be out of proportion to the volume of the wear scar. This case also is the first description of elimination kinetics of systemic titanium exposure caused by wear of a hip arthroplasty. Methods: Case report. Results: A 85-year-old male required revision after total hip arthroplasty due to aseptic loosening of the cup. A massive local adverse reaction to metal and polyethylene debris developed before revision, much larger than the implant damage would intuitively suggest. In this case, in vivo transition in wear mode from edge loading to impingement wear resulted in excessive titanium and polyethylene wear and subsequently a voluminous macrophage reaction and an excessive systemic titanium exposure, with blood concentrations showing a very long elimination half-life of more than two years. Conclusions: The volume of the wear particle reaction is dictated by the volume of the inflammatory cells, not of the wear particles. To the best of our knowledge, this is the first description of elimination kinetics in case of systemic titanium exposure. While the tissue response is caused by a sudden increase of titanium and polyethylene debris, titanium is detectable through whole blood, not serum, analysis and thus be an indicator for risk of failure due to abnormal articulation of the joint replacement. Such measurement may be useful if changes in implant position are detected radiographically. Major elevations of titanium concentrations may require revision, as for any other metal ions.

The Emerging Threat of Micro- and Nanoplastics on the Maturation and Activity of Immune Cells

With the increasing use of plastics worldwide, the amount of plastic waste being discarded has also risen. This plastic waste undergoes physical and chemical processes, breaking down into smaller particles known as microplastics (MPs) or nanoplastics (NPs). Advances in technology have enhanced our ability to detect these smaller particles, and it has been confirmed that plastics can be found in marine organisms as well as within the human body. However, research on the effects of MPs or NPs on living organisms has only recently been started, and our understanding remains limited. Studies on the immunological impacts are still ongoing, revealing that MPs and NPs can differentially affect various immune cells based on the material, size, and shape of the plastic particles. In this review, we aim to provide a comprehensive understanding of the effects of MPs and NPs on the immune system. We will also explore the methods for plastic removal through physicochemical, microbial, or biological means.

Contact Dermatitis From Biomedical Devices, Implants, and Metals-Trouble From Within

Allergic contact dermatitis is characterized by its appearance of red, raised and infiltrated, scaling or scabbed skin and intense pruritus, and distinguished from irritant contact dermatitis by its specific immune process and histopathology. Many contact allergens are low-molecular- weight chemicals including metals such as nickel, cobalt, and chromium, preservatives, and adhesives. When such materials are used internally in biomedical devices, they are similarly capable of causing sensitization and an inflammatory response. Sometimes, the reaction remains internal, and presents as swelling, pain, stiffness, decreased range of motion, and internal itching around the implant. Such reactions may, in some cases, also extend to include a localized or, rarely, systemic contact dermatitis indicative of the same process. This review will present an overview of reported skin and local internal reactions to orthopedic implants, which are the largest category of implanted internal metal devices. Immune reactions to smaller categories of medical appliances include cardiac devices and vascular stents, neuromodulation devices, diabetic appliances, Nuss bar surgery for pectus excavatum, and dental and spinal implants. We will review the available diagnostic tools, the consensus on interpretation, and reported strategies for treatment.

Case Series: Hepatic and Splenic Titanium Dioxide Deposition in Association With Intravenous Drug Use

ABSTRACT

Titanium dioxide is a versatile compound that is found in a variety of consumer products, medical hardware, and pharmaceuticals. Although oral and topical ingestion of this compound is common, intravenous introduction is much less common. We present three cases where significant titanium dioxide deposits were identified in liver and splenic tissue of three decedents, all of whom died of illicit drug overdose in the same geographic area and had fentanyl and its metabolites in blood on postmortem toxicologic testing. At autopsy, liver sections had a granular texture with fine white stippling grossly, and histologic examination of hepatic and splenic tissues showed scattered patches of black granular material with pink birefringence. Energy-dispersive x-ray spectroscopy performed on these tissues revealed the presences of clusters of titanium dioxide. Immunohistochemical staining of both the liver and spleen with CD68 confirmed the titanium dioxide clusters were within macrophages. Intravenous titanium dioxide nanoparticle elimination studies in rats suggest a time sensitive period for this elimination, with a transient period of pigment deposition between 1-58 days following injection. If a time-dependent link between titanium dioxide pigment deposition within tissues and intravenous drug use can be shown, this could be a valuable tool for Pathologists.

In vivo assessment of TiO2 based wear nanoparticles in periprosthetic tissues

A multimodal approach combining inductively coupled plasma mass spectrometry (ICP-MS), single-particle ICP-MS (spICP-MS), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) and Raman spectroscopy enabled a deeper insight into the balance between total titanium (Ti), the soluble titanium fraction and titanium dioxide based particle fraction levels in periprosthetic tissues collected from patients undergoing revision surgery. Hydrofluoric acid usage in the sample digestion allowed for complete digestion of TiO2 particles, thus enabling accurate estimation of total Ti levels. The TiO2 fraction represents 38-94% of the titanium load in the six samples where particles were detected, and the fraction is present mainly in samples from patients with aseptically loosened total hip arthroplasty. Further attention was given to this fraction determining the elemental composition, particle count, particle size and modification of TiO2. The spICP-MS analysis confirmed the presence of the TiO2-derived (nano)particles (NPs) with a 39- to 187-nm median size and particle count up to 2.3 × 1011 particles per gram of tissue. On top of that, the SEM-EDS confirmed the presence of the TiO2 nanoparticles with 230-nm median size and an anatase crystal phase was determined by Raman spectroscopy. This study presents a novel multimodal approach for TiO2 particle determination and characterization in tissue samples and is the first in vivo study of this character.

Chronic exposure to TiO2 micro- and nano particles: A biochemical and histopathological experimental study

The aim of this work was to analyze the effects of long-term exposure to titanium dioxide (TiO2) micro- (MPs) and nanoparticles (NPs) (six and 12 months) on the biochemical and histopathological response of target organs using a murine model. Male Wistar rats were intraperitoneally injected with a suspension of TiO2 NPs (5 nm; TiO2-NP5 group) or MPs (45 μm; TiO2-NP5 group); the control group was injected with saline solution. Six and 12 months post-injection, titanium (Ti) concentration in plasma and target organs was determined spectrometrically (ICP-MS). Blood smears and organ tissue samples were evaluated by light microscopy. Liver and kidney function was evaluated using serum biochemical parameters. Oxidative metabolism was assessed 6 months post-injection (determination of superoxide anion by nitroblue tetrazolium (NBT) test, superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation, and paraoxonase 1). Titanium (Ti) concentration in target organs and plasma was significantly higher in the TiO2-exposed groups than in the control group. Histological evaluation showed the presence of titanium-based particles in the target organs, which displayed no structural alterations, and in blood monocytes. Oxidative metabolism analysis showed that TiO2 NPs were more reactive over time than MPs (p < .05) and mobilization of antioxidant enzymes and membrane damage varied among the studied organs. Clearance of TiO2 micro and nanoparticles differed among the target organs, and lung clearance was more rapid than clearance from the lungs and kidneys (p < .05). Conversely, Ti concentration in plasma increased with time (p < .05). In conclusion, neither serum biochemical parameters nor oxidative metabolism markers appear to be useful as biomarkers of tissue damage in response to TiO2 micro- and nanoparticle deposits at chronic time points.

Prosthetic Metals: Release, Metabolism and Toxicity

The development of metallic joint prostheses has been ongoing for more than a century alongside advancements in hip and knee arthroplasty. Among the materials utilized, the Cobalt-Chromium-Molybdenum (Co-Cr-Mo) and Titanium-Aluminum-Vanadium (Ti-Al-V) alloys are predominant in joint prosthesis construction, predominantly due to their commendable biocompatibility, mechanical strength, and corrosion resistance. Nonetheless, over time, the physical wear, electrochemical corrosion, and inflammation induced by these alloys that occur post-implantation can cause the release of various metallic components. The released metals can then flow and metabolize in vivo, subsequently causing potential local or systemic harm. This review first details joint prosthesis development and acknowledges the release of prosthetic metals. Second, we outline the metallic concentration, biodistribution, and elimination pathways of the released prosthetic metals. Lastly, we discuss the possible organ, cellular, critical biomolecules, and significant signaling pathway toxicities and adverse effects that arise from exposure to these metals.

Selection, identification and evaluation of optimal reference genes in Chinese sturgeon (Acipenser sinensis) under polypropylene microplastics stress

Polypropylene microplastics (PP-MPs) are emerging environmental contaminants that have the potential to cause adverse effects on aquatic organisms. Reverse transcriptase quantitative real-time polymerase chain reaction (RT-qPCR) is a valuable tool for assessing the gene expression profiles under PP-MPs stress. To obtain an accurate gene expression profile of tissue inflammation and apoptosis that reflects the molecular mechanisms underlying the impact of PP-MPs on Chinese sturgeon, identifying reliable reference genes is crucial for RT-qPCR analysis. In this study, we constructed an experiment model of Chinese sturgeon exposed to PP-MPs, assessed the pathological injury, metabolic profile responses and oxidative stress in liver, evaluated the reliability of 8 reliable reference genes by 4 commonly used algorithms including GeNorm, NormFinder, BeatKeeper, Delta Ct, and then analyzed the performance of inflammatory response genes in liver, spleen and kidney with the best reference gene. HE staining revealed that the cytoplasm full small vacuoles and nucleus diameter increased were occurred in the liver cell of PP-MPs in treatment groups. Additionally, oxidative and biochemical parameters were significantly changes in the liver of treatment groups. For the reference genes in PP-MPs exposure experiments, this study screening the optimal reference genes including: EF1α and GAPDH for liver and spleen, and GAPDH and RPS18 for kidney. Besides, 2 inflammatory response genes (NLRP3, TNF-α) were chosen to assess the optimal reference genes using the least stable reference gene (TUB) as a control, verified the practicality of the select reference genes in different tissues. We also found that the low concentration of PP-MPs could induce the liver tissue damage and inflammatory response in Chinese sturgeon. Our study initially evaluated the impact of short-time exposure with PP-MPs in Chinese sturgeon and provided 3 sets of validated optimal reference genes in Chinese sturgeon exposure to PP-MPs.

Microplastic-mediated new mechanism of liver damage: From the perspective of the gut-liver axis

Microplastics (MPs) are environmental contaminants that are present in all environments and can enter the human body, accumulate in various organs, and cause harm through the ingestion of food, inhalation, and dermal contact. The connection between bowel and liver disease and the interplay between gut, liver, and flora has been conceptualized as the "gut-liver axis". Microplastics can alter the structure of microbial communities in the gut and the liver can also be a target for microplastic invasion. Numerous studies have found that when MPs impair human health, they not only promote dysbiosis of the gut microbiota and disruption of the gut barrier but also cause liver damage. For this reason, the gut-liver axis provides a new perspective in understanding this toxic response. The cross-talk between MPs and the gut-liver axis has attracted the attention of the scientific community, but knowledge about whether MPs cause gut-liver interactions through the gut-liver axis is still very limited, and the effect of MPs on liver injury is not well understood. MPs can directly induce microbiota disorders and gut barrier dysfunction. As a result, harmful bacteria and metabolites in the gut enter the blood through the weak intestinal barrier (portal vein channel along the gut-liver axis) and reach the liver, causing liver damage (inflammatory damage, metabolic disorders, oxidative stress, etc.). This review provides an integrated perspective of the gut-liver axis to help conceptualize the mechanisms by which MP exposure induces gut microbiota dysbiosis and hepatic injury and highlights the connection between MPs and the gut-liver axis. Therefore, from the perspective of the gut-liver axis, targeting intestinal flora is an important way to eliminate microplastic liver damage.

Granulomatous liver diseases

A granuloma is a discrete collection of activated macrophages and other inflammatory cells. Hepatic granulomas can be a manifestation of localized liver disease or be a part of a systemic process, usually infectious or autoimmune. A liver biopsy is required for the detection and evaluation of granulomatous liver diseases. The prevalence of granulomas on liver biopsy varies from 1% to 15%. They may be an incidental finding in an asymptomatic individual, or they may represent granulomatous hepatitis with potential to progress to liver failure, or in chronic disease, to cirrhosis. This review focuses on pathogenesis, histological features of granulomatous liver diseases, and most common etiologies, knowledge that is essential for timely diagnosis and intervention.

Mettl3‑mediated m6A RNA methylation regulates osteolysis induced by titanium particles

Peri‑prosthetic osteolysis (PPO) induced by wear particles is considered the primary cause of titanium prosthesis failure and revision surgery. The specific molecular mechanisms involve titanium particles inducing multiple intracellular pathways, which impact disease prevention and the targeted therapy of PPO. Notably, N6‑methyladenosine (m6A) serves critical roles in epigenetic regulation, particularly in bone metabolism and inflammatory responses. Thus, the present study aimed to determine the role of RNA methylation in titanium particle‑induced osteolysis. Results of reverse transcription‑quantitative PCR (RT‑qPCR), western blotting, ELISA and RNA dot blot assays revealed that titanium particles induced osteogenic inhibition and proinflammatory responses, accompanied by the reduced expression of methyltransferase‑like (Mettl) 3, a key component of m6A methyltransferase. Specific lentiviruses vectors were employed for Mettl3 knockdown and overexpression experiments. RT‑qPCR, western blotting and ELISA revealed that the knockdown of Mettl3 induced osteogenic inhibition and proinflammatory responses comparable with that induced by titanium particle, while Mettl3 overexpression attenuated titanium particle‑induced cellular reactions. Methylated RNA immunoprecipitation‑qPCR results revealed that titanium particles mediated the methylation of two inhibitory molecules, namely Smad7 and SMAD specific E3 ubiquitin protein ligase 1, via Mettl3 in bone morphogenetic protein signaling, leading to osteogenic inhibition. Furthermore, titanium particles induced activation of the nucleotide binding oligomerization domain 1 signaling pathway through methylation regulation, and the subsequent activation of the MAPK and NF‑κB pathways. Collectively, the results of the present study indicated that titanium particles utilized Mettl3 as an upstream regulatory molecule to induce osteogenic inhibition and inflammatory responses. Thus, the present study may provide novel insights into potential therapeutic targets for aseptic loosening in titanium prostheses.

Identification and analysis of microplastics in human lower limb joints

Microplastics (MPs) have been detected in various human tissues, including the liver, placenta, and blood. However, studies about MPs in the human locomotor system are limited. This study evaluated the presence of MPs in the synovium of 45 patients undergoing hip or knee arthroplasty using micro-Fourier transform infrared spectroscopy, scanning electron microscopy, and Raman microscopy and investigated their association with clinical indicators and local cellular responses. A total of 343 MPs of nine common types were identified, with a mean abundance of 5.24 ± 2.07 particles/g and ranging from 1.16 to 10.77 particles/g. Although there was no clear correlation between MP abundance and demographics, MP abundance was higher in hip samples than in knee samples. In addition, a potential association was observed between MP abundance and specific clinical diagnoses. Transcriptomic analysis revealed that a three-fold increase in MP abundance corresponded to enhanced local cellular stress responses, particularly heat shock protein reactions. Our findings demonstrate the presence of MPs in human joints and suggest that further studies are needed to explore the intricate associations between MPs and anatomical location, clinical diagnosis, and local cellular responses.

Serum Titanium Levels Remain Elevated But Urine Titanium is Undetectable in Children With Early Onset Scoliosis Undergoing Growth-Friendly Surgical Treatment: A Prospective Study

BACKGROUND

Elevated serum titanium levels have been found in patients with early onset scoliosis (EOS) treated with traditional growing rods (TGR), magnetically controlled growing rods (MCGR), and vertical expandable prosthetic titanium rib (VEPTR). No studies have investigated whether serum titanium remains persistently elevated and if titanium is excreted. Our purpose was to compare serum titanium levels in patients with EOS with growth-friendly instrumentation to age-matched controls and evaluate urine titanium and serial serum titanium levels in patients with EOS.

METHODS

This was a prospective case-control study. Patients with EOS with TGR, MCGR, or VEPTR underwent urine titanium and serial serum titanium collection at a minimum 6-month interval. Control patients did not have a history of metal implant insertion and underwent serum titanium collection before fracture fixation.

RESULTS

Twenty patients with EOS (6 TGR, 8 MCGR, and 6 VEPTR) and 12 controls were analyzed. The control group had no detectable serum titanium (0 ng/mL), whereas the patients with EOS had a median serum titanium of 4.0 ng/mL ( P < 0.001). Analysis of variance showed significantly higher median serum titanium levels in the MCGR and VEPTR groups than the TGR group at time point 1 (5.5 vs 6.0 vs 2.0 ng/mL, P = 0.01) and time point 2 (6.5 vs 7.5 vs 2.0 ng/mL, P < 0.001). Binary comparisons showed a significant difference in serum titanium level between TGR and MCGR (time point 1: P = 0.026, time point 2: P = 0.011) and TGR and VEPTR (time point 1: P = 0.035, time point 2: P = 0.003). However, there was no difference between MCGR and VEPTR (time point 1: P = 0.399, time point 2: P = 0.492) even though the VEPTR group had a longer duration of follow-up ( P = 0.001) and a greater number of lengthenings per patient at the first serum collection ( P = 0.016). No patients with EOS had detectable urine titanium.

CONCLUSIONS

Patients with EOS treated with titanium alloy growth-friendly instrumentation had elevated serum titanium levels compared with age-matched controls that persisted over time with no evidence of renal excretion. Additional studies are necessary to assess for local and systemic accumulation of titanium and the significance of long-term exposure to titanium in growing children.

LEVEL OF EVIDENCE

Level III, therapeutic.

Dental Implant Corrosion Products May Accumulate in the Human Body

BACKGROUND

Corrosion products resulting from the degradation of the dental implant surface due to biological fluids and infection may accumulate in the body and lead to clinical consequences.

PURPOSE

The primary aim of this study is to measure the accumulation of dental implant corrosion products in the human body and the secondary aim is to estimate the association between corrosion products and fatigue.

STUDY DESIGN, SETTING, SAMPLE

This study was designed as a prospective cross-sectional and was conducted with patients presenting at to the Department of Oral and Maxillofacial Surgery. The study included patients with Grade IV dental implants made of pure titanium (Ti) at the bone level and Grade V abutments composed of Ti, aluminum (Al), and vanadium (V). Individuals possessing different metallic implants and those prone to metal exposure were not included in the study. Blood and hair samples were procured from each participant and subsequently analyzed.

PREDICTOR VARIABLES

The predictor variable is implant exposure, and it was divided into 3 groups; Group I, patients with healthy dental implants; Group II, patients with peri-implantitis; Control Group, individuals without dental implants.

MAIN OUTCOME VARIABLES

The primary outcome variables are Al, Ti, V levels in blood and hair samples and the secondary outcome variable is the fatigue questionnaire score.

COVARIATES

Age and gender, along with the dental implant number and duration of exposure within the study groups, are utilized as covariates.

ANALYSES

Groups were compared using the Kruskal-Wallis and Mann-Whitney U-tests. Spearman's correlation coefficient determined relationships between groups, signifying significance with P values <.05.

RESULTS

The sample consisted of 30 patients aged 18 to 68, with 53% being female and 47% male. The differences among the 3 groups in the median values of blood Ti, V; hair Al, Ti, V; and fatigue questionnaire scores were not statistically significant (P > .05). However, the median blood Al value was statistically higher in Group II (P < .05).

CONCLUSIONS AND RELEVANCE

While the presence of healthy dental implants may not affect the accumulation of Al, Ti, and V within the body, patients with peri-implantitis exhibited elevated blood Al levels, possibly due to infection influencing the corrosion process.

Long-term exposure to polystyrene microplastics induces hepatotoxicity by altering lipid signatures in C57BL/6J mice

It is estimated that the life of plastics is hundreds to thousands of years, their lasting properties making plastic debris absorbing toxic chemicals and degrading into microplastics (MPs). The purpose of this study was to explore the effects of exposure to different size (0.08 and 0.5 μm) polystyrene (PS) in mice. After 16 weeks of exposure, it was found that PS-MPs could be identified in the liver. No effect of PS-MPs treatment on body weight was observed. PS-MPs exposure disturbed lipids and lipid-like molecule metabolisms and perturbed the citrate cycle and oxidative phosphorylation. Meanwhile, isocitrate dehydrogenase (ICDHc), nicotinamide adenine dinucleotide -malate dehydrogenase (NAD-MDH), succinate dehydrogenase (SDH), α ketoglutarate dehydrogenase (α-KGDH) activities and adenosine triphosphate (ATP) level were obviously affected by PS-MPs treatment. In addition, significant differences were recorded in catalase (CAT) and malondialdehyde (MDA) levels, indicating that PS-MPs exposure induced an oxidative stress in the liver. In conclusion, our present study provided the first evidence of: (a) long-term exposure to PS-MPs lead to PS-MPs accumulated in the liver and results in liver injury; (b) long-term exposure to PS-MPs disturbs lipids and lipid-like molecule metabolisms; (c) long-term exposure to PS-MPs perturbs citrate cycle and oxidative phosphorylation and leads to oxidative stress in the liver.

Airborne microplastics: A narrative review of potential effects on the human respiratory system

There has been growing evidence showing the widespread of airborne microplastics (AMPs) in many regions of the world, raising concerns about their impact on human health. This review aimed to consolidate recent literature on AMPs regarding their physical and chemical characteristics, deposition in the human respiratory tract, translocation, occurrence from human studies, and toxic effects determined in vitro and in vivo. The physical characteristics influence interactions with cell membranes, cellular internalization, accumulation, and cytotoxicity resulting from cell membrane damage and oxidative stress. In addition, prolonged exposure to AMP-associated toxic chemicals might lead to significant health effects. Most toxicological assessments of AMPs in vitro and in vivo have demonstrated that oxidative stress and inflammation are major mechanisms of action for their toxic effects. Elevated reactive oxygen species production could lead to mitochondrial dysfunction, inflammatory responses, and subsequent apoptosis in experimental models. To date, there has been some evidence suggesting exposure in humans. However, the data are still insufficient, and adverse human health effects need to be investigated. Future research on the existence, exposure, and health effects of AMPs is required for developing preventive and mitigation measures to protect human health.

Metal-on-Metal Hip Arthroplasty: A Comprehensive Review of the Current Literature

Metal-on-metal (MoM) total hip arthroplasty has been widely used since the end of the 20th century, although rates have now decreased due to concerns regarding adverse reactions and failure rates. The MoM implant has been replaced with other materials, such as ceramic-on-ceramic (CoC) and metal-on-polyethylene (MoP). This literature review looks at the past and present use of MoM prostheses to assess whether the turn away from MoM use is justified. Online literature searches were performed on PubMed, Ovid Medical Literature Analysis and Retrieval System Online (MEDLINE), and Web of Science online databases using the search terms "MoM and (ARMD and ALVAL)" (ARMD: adverse reaction to metal debris; ALVAL: aseptic lymphocyte-dominant vasculitis-associated lesion). A total of 64 relevant titles were included in the review. Although risk factors for adverse reactions and the causes of ARMD are generally agreed upon, more work is required to further understand the specific thresholds of blood metal ion levels that can be used to consistently identify ARMD and excessive metal wear-debris in patients who have not had their MoM implants revised. Metal-on-metal devices are not an acceptable option for total hip arthroplasties (THAs) in their current formulation due to the high rate and risk of ARMD. Some MoM hip resurfacing operations are appropriate for very carefully selected patients who are fully aware of the risks posed by the implant. It is recommended that device-specific thresholds for metal ion levels be developed to identify patients at risk of ARMD locally and systemically while using auxiliary tools to assist diagnosis, such as metal artefact reduction sequences (MARS)-MRI and hip scoring tools. Further work should investigate device-specific blood metal ion levels, the systemic effects of raised metal ion concentrations secondary to MoM arthroprosthetic wear, and the potential risks of ARMD caused by wear from tapered stems (including the implications this has for patients with CoC and MoP prostheses).

Updates on Biomaterials Used in Total Hip Arthroplasty (THA)

One of the most popular and effective orthopedic surgical interventions for treating a variety of hip diseases is total hip arthroplasty. Despite being a radical procedure that involves replacing bone and cartilaginous surfaces with biomaterials, it produces excellent outcomes that significantly increase the patient's quality of life. Patient factors and surgical technique, as well as biomaterials, play a role in prosthetic survival, with aseptic loosening (one of the most common causes of total hip arthroplasty failure) being linked to the quality of biomaterials utilized. Over the years, various biomaterials have been developed to limit the amount of wear particles generated over time by friction between the prosthetic head (metal alloys or ceramic) and the insert fixed in the acetabular component (polyethylene or ceramic). An ideal biomaterial must be biocompatible, have a low coefficient of friction, be corrosion resistant, and have great mechanical power. Comprehensive knowledge regarding what causes hip arthroplasty failure, as well as improvements in biomaterial quality and surgical technique, will influence the survivability of the prosthetic implant. The purpose of this article was to assess the benefits and drawbacks of various biomaterial and friction couples used in total hip arthroplasties by reviewing the scientific literature published over the last 10 years.

Quantification of titanium and zirconium elements in oral mucosa around healthy dental implants: a case-control pilot study

OBJECTIVES

Metallic particles are detected in different sites of the oral cavity, mainly in patients with peri-implantitis lesions. The aim of this pilot study was to analyze the levels of titanium and zirconium elements in the oral mucosa around healthy implants and to investigate the impact of titanium exogenous contamination on the measurements.

MATERIALS AND METHODS

Forty-one participants were included in this three-phase study. Two groups of subjects were defined according to presence of titanium or zirconia implants (n: 20) or without any implants nor metallic restorations (n:21). Thirteen patients (n: 5 with zirconia implant; n: 3 with titanium implants; n: 5 control group) took part to the first part designed to optimize and validate the method of detecting titanium (Ti) and zirconium (Zr) elements in the oral mucosa and gingival tissues by the Inductively Coupled Plasma Mass Spectrometry (ICPMS). The second phase compared the levels of Ti and Zr concentrations in patients with implants (n: 12) and without implants (n: 6) who were controlled for their intake of titanium dioxide (TiO2). The last step included ten control subjects without any metallic devices to measure the concentration of Ti and Zr before and after having candies containing TiO2.

RESULTS

In the first phase, concentrations of Ti and Zr were below the limit of detection (LOD) in most cases, 0.18 μg/L and 0.07 μg/L respectively. In the titanium group, two out of three subjects displayed concentrations above the LOD, 0.21 μg/L and 0.66 μg/L. Zr element was only found in patients with zirconia implants. After controlling the intake of TiO2, all concentrations of Ti and Zr were below the limit of quantification (LOQ). Moreover, in patients with no implants, the Ti concentration in gingiva cells was superior for 75% of the samples after having a TiO2 diet.

CONCLUSIONS

Zirconium was only found in patients with zirconia implants, whereas titanium was detected in all groups even in subjects with no titanium implants. Zirconium and titanium elements were not detected in patients who were controlled for their intake of food and their use of toothpaste irrespective of the presence of implants or not. For 70% of the patients, the titanium detection was directly influenced by the intake of TiO2 contained candies.

CLINICAL RELEVANCE

When analyzing titanium particles, it is necessary to pay attention to the risk of contamination bias brought by external products. When this parameter was controlled, no titanium particles were detected around clinically healthy implants.

Case report and review: Angiosarcoma with thrombocytopenia after total hip arthroplasty

Total hip arthroplasty (THA) is a common treatment for osteoarthritis and is also performed for other conditions, such as secondary arthritis due to developmental dysplasia of the hip. Various THA types may be complicated by osteolysis and an inflammatory pseudotumor due to an adverse reaction to metal debris. Rarely, THA has been associated with malignant tumors, but their causality remains unclear. In this case report, we describe a female patient with developmental dysplasia of the hip. She had undergone left metal-on-polyethylene THA, acetabular revision of the THA, and left total knee arthroplasty. In addition, she had a history of dyslipidemia and telangiectasia of the eyes, anemia, hiatal hernia, and pleuritis. A THA-associated mass (suspected to be a pseudotumor) had been detected during a previous hospital admission due to pleuritis. She was hospitalized due to swelling in her left lower limb, fatigue, and bruises. A clinical examination revealed anemia, thrombocytopenia, and growth of the suspected pseudotumor. Within 6 weeks, she presented with bleeding of the oral mucosa, hemoptysis, melena, severe thrombocytopenia that did not respond to treatment, elevated D-dimer and C-reactive protein levels, severe pain, increased osteolysis, and fractures around the THA. Infection or malignancy was suspected, but two trocar biopsies suggested an inflammatory pseudotumor. Since her anemia and thrombocytopenia were considered to have been caused by an inflammatory process within the suspected pseudotumor, her suspected pseudotumor and all THA components were surgically removed. However, she developed severe alveolar hemorrhaging and hypoxia and died 2 weeks after her surgery. Histopathological analysis of her surgical and autopsy samples revealed highly malignant angiosarcoma. Although individual cases of malignancies associated with THA have been reported, the literature lacks a clear association between THA and increased cancer risk. Most pseudotumors are non-malignant. The patient's case presented in this report exemplifies the challenges to the differential diagnosis of a THA-associated pseudotumor and rare angiosarcoma. Atypically rapid tumor growth, severe osteolysis, and deterioration in the general wellbeing suggest a malignant disease.

Urchin-like ceria nanoparticles for enhanced gene therapy of osteoarthritis

Osteoarthritis (OA) is the most common degenerative joint disease in the world. Gene therapy based on delivering microRNAs (miRNAs) into cells has potential for the treatment of OA. However, the effects of miRNAs are limited by the poor cellular uptake and stability. Here, we first identify a type of microRNA-224-5p (miR-224-5p) from clinical samples of patients with OA that can protect articular cartilage from degeneration and further synthesize urchin-like ceria nanoparticles (NPs) that can load miR-224-5p for enhanced gene therapy of OA. Compared with traditional sphere ceria NPs, the thorns of urchin-like ceria NPs can efficiently promote the transfection of miR-224-5p. In addition, urchin-like ceria NPs have excellent performance of scavenging reactive oxygen species (ROS), which can regulate the microenvironment of OA to further improve the gene treatment of OA. The combination of urchin-like ceria NPs and miR-224-5p not only exhibits favorable curative effect for OA but also provides a promising paradigm for translational medicine.

Research advances of microplastics and potential health risks of microplastics on terrestrial higher mammals: a bibliometric analysis and literature review

Microplastics (MPs) have become increasingly serious global problems due to their wide distribution and complicated impacts on living organisms. To obtain a comprehensive overview of the latest research progress on MPs, we conducted a bibliometric analysis combined with a literature review. The results showed that the number of studies on MPs has grown exponentially since 2010. Recently, the hotspot on MPs has shifted to terrestrial ecosystems and biological health risks, including human health risks. In addition, the toxic effects, identification and quantification of MPs are relatively new research hotspots. We subsequently provide a review of MPs studies related to health risks to terrestrial higher mammals and, in particular, to humans, including detection methods and potential toxicities based on current studies. Currently, MPs have been found existing in human feces, blood, colon, placenta and lung, but it is still unclear whether this is associated with related systemic diseases. In vivo and in vitro studies have demonstrated that MPs cause intestinal toxicity, metabolic disruption, reproductive toxicity, neurotoxicity, immunotoxicity through oxidative stress, apoptosis and specific pathways, etc. Notably, in terms of combined effects with pollutants and neurotoxicity, the effects of MPs are still controversial. Future attention should be paid to the detection and quantification of MPs in human tissues, exploring the combined effects and related mechanisms of MPs with other pollutants and clarifying the association between MPs and the development of pre-existing diseases. Our work enhances further understanding of the potential health risks of MPs to terrestrial higher mammals.

The effects of size and surface functionalization of polystyrene nanoplastics on stratum corneum model membranes: An experimental and computational study

Nanoplastics are mainly generated from the decomposition of plastic waste and artificial production and have attracted much attention due to their wide distribution in the environment and the potential risk for humans. As the largest organ of the human body, the skin is inevitably in contact with nanoplastics. Stratum corneum is the first barrier when the skin is exposed to nanoplastics. However, little is known about the interactions between nanoplastics and stratum corneum. Here, the effects of particle size and surface functionalization (amino-modified and carboxy-modified) of polystyrene nanoplastics on the stratum corneum models were studied by Langmuir monolayer and molecular dynamics simulations. An equimolar mixture of ceramide/cholesterol/free fatty acid was used to mimic stratum corneum intercellular lipids. The Langmuir monolayer studies demonstrated that the larger size and surface functionalization of polystyrene nanoplastics significantly reduced the stability of stratum corneum lipid monolayer in a concentration-dependent fashion. Simulation results elucidated that functionalized polystyrene oligomers had a stronger interaction with lipid components of the stratum corneum model membrane. The cell experiments also indicated that functionalized polystyrene nanoplastics, especially for amino-modified polystyrene nanoplastics, had significant cytotoxicity on normal human dermal fibroblast cells. Our results provide fundamental information and the basis for a deeper understanding of the health risks of nanoplastics to humans.

The effects of adsorbed benzo(a)pyrene on dynamic behavior of polystyrene nanoplastics through phospholipid membrane: A molecular simulation study

Nanoplastics (NPs) are mainly generated from the decomposition of plastic waste and industrial production, which have attracted much attention due to the potential risk for humans. The ability of NPs to penetrate different biological barriers has been proved, but the understanding of molecular details is very limited, especially for organic pollutant-NP combinations. Here, we investigated the uptake process of polystyrene NPs (PSNPs) combined with benzo(a)pyrene (BAP) molecules by dipalmitoylphosphatidylcholine (DPPC) bilayers by molecular dynamics (MD) simulations. The results showed that the PSNPs can adsorb and accumulate BAP molecules in water phase and then carried BAP molecules to enter DPPC bilayers. At the same time, the adsorbed BAP promoted the penetration of PSNPs into DPPC bilayers effectively by hydrophobic effect. The process of BAP-PSNP combinations penetrating into DPPC bilayers can be summarized into four steps including adhesion on the DPPC bilayer surface, uptake by the DPPC bilayer, BAP molecules detached from the PSNPs, and the PSNPs depolymerized in the bilayer interior. Furthermore, the amount of adsorbed BAP on PSNPs affected the properties of DPPC bilayers directly, especially the fluidity of DPPC bilayers that determine the physiologic function. Obviously, the combined effect of PSNPs and BAP enhanced the cytotoxicity. This work not only presented a vivid transmembrane process of BAP-PSNP combinations and revealed the nature of the effects of adsorbed benzo(a)pyrene on the dynamic behavior of polystyrene nanoplastics through phospholipid membrane, but also provide some necessary information of the potential damage for organic pollutant-nanoplastic combinations on human health at a molecular level.

A critical review on recent research progress on microplastic pollutants in drinking water

Plastic pollution is an emerging issue in recent days. Persistent plastic particles reach the atmosphere, land and water by multiple pathways. Research has confirmed that the existence of plastic particles is found surprisingly everywhere, from the Artic to the Antarctic region. The probability of ingestion of plastic by all living forms is quite natural, as the whole planet's environment is polluted with microplastic particles. The bioaccumulation of microplastics is a threat and the consequences for living beings are yet to be explored. Microplastics present in different drinking water sources like rivers, lakes, treatment units etc. are studied by several researchers, covering various aspects. Research carried out by various scientists on the microplastics in different drinking water sources is highlighted in this review. In view of the previous research carried out on various aspects of microplastic particles, the necessity of a uniform protocol for qualitative and quantitative analysis of microplastic is ascertained. Microplastic pollution is an ongoing environmental concern, it must be addressed and research should be expanded.

A spectroscopic study on orthodontic aligners: First evidence of secondary microplastic detachment after seven days of artificial saliva exposure

Clear orthodontic aligners have recently seen increasing popularity. The thermoplastic materials present several advantages, even if it is known that all plastic products can be subjected to environmental and mechanical degradation, leading to the release of microplastics (MPs). Their ingestion could cause oxidative stress and inflammatory lesions. This study aims to evaluate the potential detachment of MPs by clear aligners due to mechanical friction simulated with a 7-day protocol in artificial saliva. The study was performed on orthodontic clear aligners from different manufacturers: Alleo (AL); FlexiLigner (FL); F22 Aligner (F22); Invisalign® (INV); Lineo (LIN); Arc Angel (ARC), and Ortobel Aligner (OR). For each group, two aligners were immersed in artificial saliva for 7 days and stirred for 5 h/day, simulating the physiological teeth mechanical friction. After 7 days, the artificial saliva was filtered; then, filters were analyzed by Raman Microspectroscopy (RMS) and Scanning Electron Microscopy (SEM), respectively to chemically identify the polymeric matrix and to measure the number and size of the detected MPs. RMS spectra revealed that AL, FL, LIN, ARC, and OR aligners were composed by polyethylene terephthalate, while F22 and INV ones by polyurethane. SEM analysis showed that the highest number of MPs was found in ARC and the lowest in INV (p < 0.05). As regards MPs' size, no statistically significant difference was found among groups, with most MPs ranging from 5 to 20 μm. Noteworthy, a highly significant correlation (p < 0.0001) was highlighted between the distribution of MPs size and the different typologies of aligners. This in vitro study highlighted for the first time the detachment of MPs from clear aligners due to mechanical friction. This evidence may represent a great concern in the clinical practice since it could impact human general health.

The Minderoo-Monaco Commission on Plastics and Human Health

Background

Plastics have conveyed great benefits to humanity and made possible some of the most significant advances of modern civilization in fields as diverse as medicine, electronics, aerospace, construction, food packaging, and sports. It is now clear, however, that plastics are also responsible for significant harms to human health, the economy, and the earth's environment. These harms occur at every stage of the plastic life cycle, from extraction of the coal, oil, and gas that are its main feedstocks through to ultimate disposal into the environment. The extent of these harms not been systematically assessed, their magnitude not fully quantified, and their economic costs not comprehensively counted.

Goals

The goals of this Minderoo-Monaco Commission on Plastics and Human Health are to comprehensively examine plastics' impacts across their life cycle on: (1) human health and well-being; (2) the global environment, especially the ocean; (3) the economy; and (4) vulnerable populations-the poor, minorities, and the world's children. On the basis of this examination, the Commission offers science-based recommendations designed to support development of a Global Plastics Treaty, protect human health, and save lives.

Report Structure

This Commission report contains seven Sections. Following an Introduction, Section 2 presents a narrative review of the processes involved in plastic production, use, and disposal and notes the hazards to human health and the environment associated with each of these stages. Section 3 describes plastics' impacts on the ocean and notes the potential for plastic in the ocean to enter the marine food web and result in human exposure. Section 4 details plastics' impacts on human health. Section 5 presents a first-order estimate of plastics' health-related economic costs. Section 6 examines the intersection between plastic, social inequity, and environmental injustice. Section 7 presents the Commission's findings and recommendations.

Plastics

Plastics are complex, highly heterogeneous, synthetic chemical materials. Over 98% of plastics are produced from fossil carbon- coal, oil and gas. Plastics are comprised of a carbon-based polymer backbone and thousands of additional chemicals that are incorporated into polymers to convey specific properties such as color, flexibility, stability, water repellence, flame retardation, and ultraviolet resistance. Many of these added chemicals are highly toxic. They include carcinogens, neurotoxicants and endocrine disruptors such as phthalates, bisphenols, per- and poly-fluoroalkyl substances (PFAS), brominated flame retardants, and organophosphate flame retardants. They are integral components of plastic and are responsible for many of plastics' harms to human health and the environment.Global plastic production has increased almost exponentially since World War II, and in this time more than 8,300 megatons (Mt) of plastic have been manufactured. Annual production volume has grown from under 2 Mt in 1950 to 460 Mt in 2019, a 230-fold increase, and is on track to triple by 2060. More than half of all plastic ever made has been produced since 2002. Single-use plastics account for 35-40% of current plastic production and represent the most rapidly growing segment of plastic manufacture.Explosive recent growth in plastics production reflects a deliberate pivot by the integrated multinational fossil-carbon corporations that produce coal, oil and gas and that also manufacture plastics. These corporations are reducing their production of fossil fuels and increasing plastics manufacture. The two principal factors responsible for this pivot are decreasing global demand for carbon-based fuels due to increases in 'green' energy, and massive expansion of oil and gas production due to fracking.Plastic manufacture is energy-intensive and contributes significantly to climate change. At present, plastic production is responsible for an estimated 3.7% of global greenhouse gas emissions, more than the contribution of Brazil. This fraction is projected to increase to 4.5% by 2060 if current trends continue unchecked.

Plastic Life Cycle

The plastic life cycle has three phases: production, use, and disposal. In production, carbon feedstocks-coal, gas, and oil-are transformed through energy-intensive, catalytic processes into a vast array of products. Plastic use occurs in every aspect of modern life and results in widespread human exposure to the chemicals contained in plastic. Single-use plastics constitute the largest portion of current use, followed by synthetic fibers and construction.Plastic disposal is highly inefficient, with recovery and recycling rates below 10% globally. The result is that an estimated 22 Mt of plastic waste enters the environment each year, much of it single-use plastic and are added to the more than 6 gigatons of plastic waste that have accumulated since 1950. Strategies for disposal of plastic waste include controlled and uncontrolled landfilling, open burning, thermal conversion, and export. Vast quantities of plastic waste are exported each year from high-income to low-income countries, where it accumulates in landfills, pollutes air and water, degrades vital ecosystems, befouls beaches and estuaries, and harms human health-environmental injustice on a global scale. Plastic-laden e-waste is particularly problematic.

Environmental Findings

Plastics and plastic-associated chemicals are responsible for widespread pollution. They contaminate aquatic (marine and freshwater), terrestrial, and atmospheric environments globally. The ocean is the ultimate destination for much plastic, and plastics are found throughout the ocean, including coastal regions, the sea surface, the deep sea, and polar sea ice. Many plastics appear to resist breakdown in the ocean and could persist in the global environment for decades. Macro- and micro-plastic particles have been identified in hundreds of marine species in all major taxa, including species consumed by humans. Trophic transfer of microplastic particles and the chemicals within them has been demonstrated. Although microplastic particles themselves (>10 µm) appear not to undergo biomagnification, hydrophobic plastic-associated chemicals bioaccumulate in marine animals and biomagnify in marine food webs. The amounts and fates of smaller microplastic and nanoplastic particles (MNPs <10 µm) in aquatic environments are poorly understood, but the potential for harm is worrying given their mobility in biological systems. Adverse environmental impacts of plastic pollution occur at multiple levels from molecular and biochemical to population and ecosystem. MNP contamination of seafood results in direct, though not well quantified, human exposure to plastics and plastic-associated chemicals. Marine plastic pollution endangers the ocean ecosystems upon which all humanity depends for food, oxygen, livelihood, and well-being.

Human Health Findings

Coal miners, oil workers and gas field workers who extract fossil carbon feedstocks for plastic production suffer increased mortality from traumatic injury, coal workers' pneumoconiosis, silicosis, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer. Plastic production workers are at increased risk of leukemia, lymphoma, hepatic angiosarcoma, brain cancer, breast cancer, mesothelioma, neurotoxic injury, and decreased fertility. Workers producing plastic textiles die of bladder cancer, lung cancer, mesothelioma, and interstitial lung disease at increased rates. Plastic recycling workers have increased rates of cardiovascular disease, toxic metal poisoning, neuropathy, and lung cancer. Residents of "fenceline" communities adjacent to plastic production and waste disposal sites experience increased risks of premature birth, low birth weight, asthma, childhood leukemia, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer.During use and also in disposal, plastics release toxic chemicals including additives and residual monomers into the environment and into people. National biomonitoring surveys in the USA document population-wide exposures to these chemicals. Plastic additives disrupt endocrine function and increase risk for premature births, neurodevelopmental disorders, male reproductive birth defects, infertility, obesity, cardiovascular disease, renal disease, and cancers. Chemical-laden MNPs formed through the environmental degradation of plastic waste can enter living organisms, including humans. Emerging, albeit still incomplete evidence indicates that MNPs may cause toxicity due to their physical and toxicological effects as well as by acting as vectors that transport toxic chemicals and bacterial pathogens into tissues and cells.Infants in the womb and young children are two populations at particularly high risk of plastic-related health effects. Because of the exquisite sensitivity of early development to hazardous chemicals and children's unique patterns of exposure, plastic-associated exposures are linked to increased risks of prematurity, stillbirth, low birth weight, birth defects of the reproductive organs, neurodevelopmental impairment, impaired lung growth, and childhood cancer. Early-life exposures to plastic-associated chemicals also increase the risk of multiple non-communicable diseases later in life.

Economic Findings

Plastic's harms to human health result in significant economic costs. We estimate that in 2015 the health-related costs of plastic production exceeded $250 billion (2015 Int$) globally, and that in the USA alone the health costs of disease and disability caused by the plastic-associated chemicals PBDE, BPA and DEHP exceeded $920 billion (2015 Int$). Plastic production results in greenhouse gas (GHG) emissions equivalent to 1.96 gigatons of carbon dioxide (CO2e) annually. Using the US Environmental Protection Agency's (EPA) social cost of carbon metric, we estimate the annual costs of these GHG emissions to be $341 billion (2015 Int$).These costs, large as they are, almost certainly underestimate the full economic losses resulting from plastics' negative impacts on human health and the global environment. All of plastics' economic costs-and also its social costs-are externalized by the petrochemical and plastic manufacturing industry and are borne by citizens, taxpayers, and governments in countries around the world without compensation.

Social Justice Findings

The adverse effects of plastics and plastic pollution on human health, the economy and the environment are not evenly distributed. They disproportionately affect poor, disempowered, and marginalized populations such as workers, racial and ethnic minorities, "fenceline" communities, Indigenous groups, women, and children, all of whom had little to do with creating the current plastics crisis and lack the political influence or the resources to address it. Plastics' harmful impacts across its life cycle are most keenly felt in the Global South, in small island states, and in disenfranchised areas in the Global North. Social and environmental justice (SEJ) principles require reversal of these inequitable burdens to ensure that no group bears a disproportionate share of plastics' negative impacts and that those who benefit economically from plastic bear their fair share of its currently externalized costs.

Conclusions

It is now clear that current patterns of plastic production, use, and disposal are not sustainable and are responsible for significant harms to human health, the environment, and the economy as well as for deep societal injustices.The main driver of these worsening harms is an almost exponential and still accelerating increase in global plastic production. Plastics' harms are further magnified by low rates of recovery and recycling and by the long persistence of plastic waste in the environment.The thousands of chemicals in plastics-monomers, additives, processing agents, and non-intentionally added substances-include amongst their number known human carcinogens, endocrine disruptors, neurotoxicants, and persistent organic pollutants. These chemicals are responsible for many of plastics' known harms to human and planetary health. The chemicals leach out of plastics, enter the environment, cause pollution, and result in human exposure and disease. All efforts to reduce plastics' hazards must address the hazards of plastic-associated chemicals.

Recommendations

To protect human and planetary health, especially the health of vulnerable and at-risk populations, and put the world on track to end plastic pollution by 2040, this Commission supports urgent adoption by the world's nations of a strong and comprehensive Global Plastics Treaty in accord with the mandate set forth in the March 2022 resolution of the United Nations Environment Assembly (UNEA).International measures such as a Global Plastics Treaty are needed to curb plastic production and pollution, because the harms to human health and the environment caused by plastics, plastic-associated chemicals and plastic waste transcend national boundaries, are planetary in their scale, and have disproportionate impacts on the health and well-being of people in the world's poorest nations. Effective implementation of the Global Plastics Treaty will require that international action be coordinated and complemented by interventions at the national, regional, and local levels.This Commission urges that a cap on global plastic production with targets, timetables, and national contributions be a central provision of the Global Plastics Treaty. We recommend inclusion of the following additional provisions:The Treaty needs to extend beyond microplastics and marine litter to include all of the many thousands of chemicals incorporated into plastics.The Treaty needs to include a provision banning or severely restricting manufacture and use of unnecessary, avoidable, and problematic plastic items, especially single-use items such as manufactured plastic microbeads.The Treaty needs to include requirements on extended producer responsibility (EPR) that make fossil carbon producers, plastic producers, and the manufacturers of plastic products legally and financially responsible for the safety and end-of-life management of all the materials they produce and sell.The Treaty needs to mandate reductions in the chemical complexity of plastic products; health-protective standards for plastics and plastic additives; a requirement for use of sustainable non-toxic materials; full disclosure of all components; and traceability of components. International cooperation will be essential to implementing and enforcing these standards.The Treaty needs to include SEJ remedies at each stage of the plastic life cycle designed to fill gaps in community knowledge and advance both distributional and procedural equity.This Commission encourages inclusion in the Global Plastic Treaty of a provision calling for exploration of listing at least some plastic polymers as persistent organic pollutants (POPs) under the Stockholm Convention.This Commission encourages a strong interface between the Global Plastics Treaty and the Basel and London Conventions to enhance management of hazardous plastic waste and slow current massive exports of plastic waste into the world's least-developed countries.This Commission recommends the creation of a Permanent Science Policy Advisory Body to guide the Treaty's implementation. The main priorities of this Body would be to guide Member States and other stakeholders in evaluating which solutions are most effective in reducing plastic consumption, enhancing plastic waste recovery and recycling, and curbing the generation of plastic waste. This Body could also assess trade-offs among these solutions and evaluate safer alternatives to current plastics. It could monitor the transnational export of plastic waste. It could coordinate robust oceanic-, land-, and air-based MNP monitoring programs.This Commission recommends urgent investment by national governments in research into solutions to the global plastic crisis. This research will need to determine which solutions are most effective and cost-effective in the context of particular countries and assess the risks and benefits of proposed solutions. Oceanographic and environmental research is needed to better measure concentrations and impacts of plastics <10 µm and understand their distribution and fate in the global environment. Biomedical research is needed to elucidate the human health impacts of plastics, especially MNPs.

Summary

This Commission finds that plastics are both a boon to humanity and a stealth threat to human and planetary health. Plastics convey enormous benefits, but current linear patterns of plastic production, use, and disposal that pay little attention to sustainable design or safe materials and a near absence of recovery, reuse, and recycling are responsible for grave harms to health, widespread environmental damage, great economic costs, and deep societal injustices. These harms are rapidly worsening.While there remain gaps in knowledge about plastics' harms and uncertainties about their full magnitude, the evidence available today demonstrates unequivocally that these impacts are great and that they will increase in severity in the absence of urgent and effective intervention at global scale. Manufacture and use of essential plastics may continue. However, reckless increases in plastic production, and especially increases in the manufacture of an ever-increasing array of unnecessary single-use plastic products, need to be curbed.Global intervention against the plastic crisis is needed now because the costs of failure to act will be immense.

Allergic reaction and metal hypersensitivity after shoulder joint replacement

PURPOSE

Metal ion release may cause local and systemic effects and induce hypersensitivity reactions. The aim of our study is first to determine if implant-related hypersensitivity correlates to patient symptoms or not; second, to assess the rate of hypersensitivity and allergies in shoulder arthroplasty.

METHODS

Forty patients with shoulder replacements performed between 2015 and 2017 were studied with minimum 2-year follow-up; no patient had prior metal implants. Each patient underwent radiographic and clinical evaluation using the Constant-Murley Score (CMS), 22 metal and cement haptens patch testing, serum and urine tests to evaluate 12 metals concentration, and a personal occupational medicine interview.

RESULTS

At follow-up (average 45 ± 10.7 months), the mean CMS was 76 ± 15.9; no clinical complications or radiographic signs of loosening were detected; two nickel sulfate (5%), 1 benzoyl peroxide (2.5%) and 1 potassium dichromate (2.5%) positive findings were found, but all these patients were asymptomatic. There was an increase in serum aluminum, urinary aluminum and urinary chromium levels of 1.74, 3.40 and 1.83 times the baseline, respectively. No significant difference in metal ion concentrations were found when patients were stratified according to gender, date of surgery, type of surgery, and type of implant.

CONCLUSIONS

Shoulder arthroplasty is a source of metal ion release and might act as a sensitizing exposure. However, patch test positivity does not seem to correlate to hypersensitivity cutaneous manifestations or poor clinical results. Laboratory data showed small constant ion release over time, regardless of gender, type of shoulder replacement and implant used.

LEVELS OF EVIDENCE

Level II.

Aluminum Nanoparticles Affect Human Platelet Function In Vitro

Endoprostheses are prone to tribological wear and biological processes that lead to the release of particles, including aluminum nanoparticles (Al NPs). Those particles can diffuse into circulation. However, the toxic effects of NPs on platelets have not been comprehensively analyzed. The aim of our work was to investigate the impact of Al NPs on human platelet function using a novel quartz crystal microbalance with dissipation (QCM-D) methodology. Moreover, a suite of assays, including light transmission aggregometry, flow cytometry, optical microscopy and transmission electron microscopy, were utilized. All Al NPs caused a significant increase in dissipation (D) and frequency (F), indicating platelet aggregation even at the lowest tested concentration (0.5 µg/mL), except for the largest (80 nm) Al NPs. A size-dependent effect on platelet aggregation was observed for the 5-20 nm NPs and the 30-50 nm NPs, with the larger Al NPs causing smaller increases in D and F; however, this was not observed for the 20-30 nm NPs. In conclusion, our study showed that small (5-50 nm) Al NPs caused platelet aggregation, and larger (80 nm) caused a bridging-penetrating effect in entering platelets, resulting in the formation of heterologous platelet-Al NPs structures. Therefore, physicians should consider monitoring NP serum levels and platelet activation indices in patients with orthopedic implants.

FeMn with Phases of a Degradable Ag Alloy for Residue-Free and Adapted Bioresorbability

The development of bioresorbable materials for temporary implantation enables progress in medical technology. Iron (Fe)-based degradable materials are biocompatible and exhibit good mechanical properties, but their degradation rate is low. Aside from alloying with Manganese (Mn), the creation of phases with high electrochemical potential such as silver (Ag) phases to cause the anodic dissolution of FeMn is promising. However, to enable residue-free dissolution, the Ag needs to be modified. This concern is addressed, as FeMn modified with a degradable Ag-Calcium-Lanthanum (AgCaLa) alloy is investigated. The electrochemical properties and the degradation behavior are determined via a static immersion test. The local differences in electrochemical potential increase the degradation rate (low pH values), and the formation of gaps around the Ag phases (neutral pH values) demonstrates the benefit of the strategy. Nevertheless, the formation of corrosion-inhibiting layers avoids an increased degradation rate under a neutral pH value. The complete bioresorption of the material is possible since the phases of the degradable AgCaLa alloy dissolve after the FeMn matrix. Cell viability tests reveal biocompatibility, and the antibacterial activity of the degradation supernatant is observed. Thus, FeMn modified with degradable AgCaLa phases is promising as a bioresorbable material if corrosion-inhibiting layers can be diminished.

Nickel contamination after minimally-invasive repair of pectus excavatum persists after bar removal

BACKGROUND

Minimally-invasive repair of pectus excavatum (MIRPE) has been shown to be associated with high release of trace metals into patient's body. The aim of our study was to analyze the kinetics of metal contamination after MIRPE and after bar removal.

METHODS

We prospectively assessed nickel and chromium changes in blood, urine, and local tissue in patients undergoing MIRPE with stainless-steel bar(s). Baseline samples were taken prior to surgery, further samples were taken at six defined time points until 30 months after bar removal. Clinical symptoms were evaluated at the time of every sample collection.

RESULTS

28 patients were included (mean age 16.4 years). At four weeks after MIRPE and persisting up to bar removal, we found significantly elevated trace metal levels in blood and urine. Tissue nickel and chromium levels were significantly elevated at the time of bar removal. After bar removal, the concentration of trace metal in urine and the concentration of chromium in plasma decreased gradually. In contrast, nickel levels in blood further increased. Five patients showed irritative symptoms after MIRPE, all symptomatic patients had elevated metal levels.

CONCLUSIONS

Following MIRPE, we found a rapid systemic increase of nickel and chromium. Our data indicate that trace metal release could cause irritative symptoms. The prolonged elevated systemic nickel levels beyond bar removal necessitate further investigations of the long-term side effects of MIRPE.

The role of foreign body response in peri-implantitis: What is the evidence?

Historically, there has been broad consensus that osseointegration represents a homeostasis between a titanium dental implant and the surrounding bone, and that the crestal bone loss characteristic of peri-implantitis is a plaque-induced inflammatory process. However, this notion has been challenged over the past decade by proponents of a theory that considers osseointegration an inflammatory process characterized by a foreign body reaction and peri-implant bone loss as an exacerbation of this inflammatory response. A key difference in these two schools of thought is the perception of the relative importance of dental plaque in the pathogenesis of crestal bone loss around implants, with obvious implications for treatment. This review investigates the evidence for a persistent foreign body reaction at osseointegrated dental implants and its possible role in crestal bone loss characteristic of peri-implantitis. Further, the role of implant-related material release within the surrounding tissue, particularly titanium particles and corrosion by-products, in the establishment and progression in peri-implantitis is explored. While it is acknowledged that these issues require further investigation, the available evidence suggests that osseointegration is a state of homeostasis between the titanium implant and surrounding tissues, with little evidence that a persistent foreign body reaction is responsible for peri-implant bone loss after osseointegration is established. Further, there is a lack of evidence for a unidirectional causative role of corrosion by-products and titanium particles as possible non-plaque related factors in the etiology of peri-implantitis.

Scaffolds Based on Poly(3-Hydroxybutyrate) and Its Copolymers for Bone Tissue Engineering (Review)

Biodegradable and biocompatible polymers are actively used in tissue engineering to manufacture scaffolds. Biomedical properties of polymer scaffolds depend on the physical and chemical characteristics and biodegradation kinetics of the polymer material, 3D microstructure and topography of the scaffold surface, as well as availability of minerals, medicinal agents, and growth factors loaded into the scaffold. However, in addition to the above, the intrinsic biological activity of the polymer and its biodegradation products can also become evident. This review provides studies demonstrating that scaffolds made of poly(3-hydroxybutyrate) (PHB) and its copolymers have their own biological activity, and namely, osteoinductive properties. PHB can induce differentiation of mesenchymal stem cells in the osteogenic direction in vitro and stimulates bone tissue regeneration during the simulation of critical and non-critical bone defects in vivo.

Bionate Biocompatibility: In Vivo Study in Rabbits

Response to foreign materials includes local tissue reaction, osteolysis, implant loosening, and migration to lymph nodes and organs. Bionate 80A human explants show minor wear and slight local tissue reaction, but we do not know the response at the spinal cord, nerve roots, lymph nodes, or distant organs. This study aims to figure out reactions against Bionate 80A when implanted at the spinal epidural space of 24 20-week-old New Zealand white rabbits. In one group of 12 rabbits, we implanted Bionate 80A on the spinal epidural space, and another group of 12 rabbits was used as the control group. We studied tissues, organs, and tissue damage markers on blood biochemistry, urine tests, and necropsy. The animals' clinical parameters and weight showed no statistically significant differences. At 3 months, the basophils increased slightly in the implant group, platelets decreased in all, and at 6 months, implanted animals showed slight eosinophilia, but none of these changes was statistically significant. External, organ, and spinal tissue examination showed neither toxic reaction, inflammatory changes, or noticeable differences between groups or survival periods. Under microscopic examination, the Bionate 80A particles induced a chronic granulomatous response always outside the dura mater, with giant multinucleated cells holding phagocytized particles and no particle migration to lymph nodes or organs. Thus, it was concluded that Bionate particles, when implanted in the rabbit lumbar epidural space, do not generate a significant reaction limited to the surrounding soft tissues with giant multinucleated cells. In addition, the particles did not cross the dura mater or migrate to lymph nodes or organs.

A review on microplastics and nanoplastics in the environment: Their occurrence, exposure routes, toxic studies, and potential effects on human health

Microplastics (MPs) and nanoplastics (NPs) are emerging environmental pollutants, having a major ecotoxicological concern to humans and many other biotas, especially aquatic animals. The physical and chemical compositions of MPs majorly determine their ecotoxicological risks. However, comprehensive knowledge about the exposure routes and toxic effects of MPs/NPs on animals and human health is not fully known. Here this review focuses on the potential exposure routes, human health impacts, and toxicity response of MPs/NPs on human health, through reviewing the literature on studies conducted in different in vitro and in vivo experiments on organisms, human cells, and the human experimental exposure models. The current literature review has highlighted ingestion, inhalation, and dermal contacts as major exposure routes of MPs/NPs. Further, oxidative stress, cytotoxicity, DNA damage, inflammation, immune response, neurotoxicity, metabolic disruption, and ultimately affecting digestive systems, immunology, respiratory systems, reproductive systems, and nervous systems, as serious health consequences.

Electrical Potentiometry with Intraoral Applications

Dental implants currently in use are mainly made of titanium or titanium alloys. As these metallic elements are immersed in an electrolytic medium, galvanic currents are produced between them or with other metals present in the mouth. These bimetallic currents have three potentially harmful effects on the patient: micro-discharges, corrosion, and finally, the dispersion of metal ions or their oxides, all of which have been extensively demonstrated in vitro. In this original work, a system for measuring the potentials generated in vivo is developed. Specifically, it is an electrogalvanic measurements system coupled with a periodontal probe that allows measurement of the potentials in the peri-implant sulcus. This device was tested and verified in vitro to guarantee its applicability in vivo. As a conclusion, this system is able to detect galvanic currents in vitro and it can be considered capable of being employed in vivo, so to assess the effects they may cause on dental implants.

Microplastic profusion in food and drinking water: are microplastics becoming a macroproblem?

Microplastics are extremely complex, and as the food chain comes full circle, it is dreaded that these could have a deleterious influence on humans. Although the risk of plastics to humans is not yet established, their occurrence in food and water destined for human consumption has been reported. The prevalence of micro-sized plastics in the ecosystem and living organisms, their trophic transfer along the food web, and the discernment of food species as competent indicators have become research priorities. The scale of the issue is massive, but what are the main culprits and causes, and could there be a solution in sight for this global problem? Despite the massive amount of research in the field, a collation of available data and pertinent hazard evaluation remains difficult. In order to identify the knowledge gaps and exposure pathways, several traits related to food chain assessment are presented with the goal of properly evaluating and managing this emerging risk. We apprehend three possible noxious consequences of small plastic particles, firstly, due to the plastic particles themselves; secondly, due to the extrication of tenacious organic pollutants adsorbed onto the plastics; and thirdly, due to the leaching of components such as monomers and additives from the plastics. The exigency for the standardization of protocols to bring about consistency in data collection and analysis, involving solutions, stakeholder costs, and benefits, are discussed. Harmonized methods will enable meticulous assessment of the impacts and threats that microplastics pose to the biota and increase the comparability between studies. We emphasize the contribution of the "honest broker" in science, providing an overarching analysis to devise the most viable solutions to microplastic pollution for private and public leadership to utilize.

Titanium or Biodegradable Osteosynthesis in Maxillofacial Surgery? In Vitro and In Vivo Performances

Osteosynthesis systems are used to fixate bone segments in maxillofacial surgery. Titanium osteosynthesis systems are currently the gold standard. However, the disadvantages result in symptomatic removal in up to 40% of cases. Biodegradable osteosynthesis systems, composed of degradable polymers, could reduce the need for removal of osteosynthesis systems while avoiding the aforementioned disadvantages of titanium osteosyntheses. However, disadvantages of biodegradable systems include decreased mechanical properties and possible foreign body reactions. In this review, the literature that focused on the in vitro and in vivo performances of biodegradable and titanium osteosyntheses is discussed. The focus was on factors underlying the favorable clinical outcome of osteosyntheses, including the degradation characteristics of biodegradable osteosyntheses and the host response they elicit. Furthermore, recommendations for clinical usage and future research are given. Based on the available (clinical) evidence, biodegradable copolymeric osteosyntheses are a viable alternative to titanium osteosyntheses when applied to treat maxillofacial trauma, with similar efficacy and significantly lower symptomatic osteosynthesis removal. For orthognathic surgery, biodegradable copolymeric osteosyntheses are a valid alternative to titanium osteosyntheses, but a longer operation time is needed. An osteosynthesis system composed of an amorphous copolymer, preferably using ultrasound welding with well-contoured shapes and sufficient mechanical properties, has the greatest potential as a biocompatible biodegradable copolymeric osteosynthesis system. Future research should focus on surface modifications (e.g., nanogel coatings) and novel biodegradable materials (e.g., magnesium alloys and silk) to address the disadvantages of current osteosynthesis systems.

Scientific and Regulatory Policy Committee Points to Consider for Medical Device Implant Site Evaluation in Nonclinical Studies

Nonclinical implantation studies are a common and often critical step for medical device safety assessment in the bench-to-market pathway. Nonclinical implanted medical devices or drug-device combination products require complex macroscopic and microscopic pathology evaluations due to the physical presence of the device itself and unique tissue responses to device materials. The Medical Device Implant Site Evaluation working group of the Society of Toxicologic Pathology's (STP) Scientific and Regulatory Policy Committee (SRPC) was tasked with reviewing scientific, technical, and regulatory considerations for these studies. Implant site evaluations require highly specialized methods and analytical schemes that should be designed on a case-by-case basis to address specific study objectives. Existing STP best practice recommendations can serve as a framework when performing nonclinical studies under Good Laboratory Practices and help mitigate limitations in standards and guidances for implant evaluations (e.g., those from the International Organization for Standardization [ISO], ASTM International). This article integrates standards referenced by sponsors and regulatory bodies with practical pathology evaluation methods for implantable medical devices and combination products. The goal is to ensure the maximum accuracy and scientific relevance of pathology data acquired during a medical device or combination drug-device implantation study.

Environmental health impacts of microplastics exposure on structural organization levels in the human body

The ubiquitous prevalence of microplastics pollution has raised concerns about microplastics' potential risks and impacts on the global environment. However, the potential human health risks and impacts of microplastics remain largely unexplored. By providing an overview regarding the interaction of microplastics and human health, this review extends current knowledge on the potential impacts of microplastics pollution on humans from an environmental health perspective. The paper firstly presents the characteristics of microplastics as well as the status of global microplastics pollution. As for human health, the potential hazards of microplastics are reflected by toxic chemical components, vectors of contaminants, and physical damage. Extensive microplastic pollution on ecosystems due to human activities leads to inevitable human exposure, which may occur by dietary, inhalation and/or skin contact. Accordingly, microplastics exposure is closely associated with human health. This study explores the potential interactions of microplastics with the biological organization at various levels, including chemical, cellular, tissue, organ, and system levels. The review concludes by highlighting five urgent perspectives and implications for future research on microplastics: 1) Developing a standard terminology and research methods; 2) Reinforcing microplastics pollution governance; 3) Exploring innovative strategies and technologies; 4) Engaging the public and change behaviour; and 5) Adopting a transdisciplinary approach.

Status and prospects of atmospheric microplastics: A review of methods, occurrence, composition, source and health risks

The global pollution of microplastics (MPs) has attracted widespread attention, and the atmosphere was an indispensable media for the global transmission of MPs. With the growing awareness of MPs, atmospheric microplastics (AMPs) have been proposed as a new topic in recent years. Compared with the extensive studies on MPs in Marine and terrestrial environments, the studies of AMPs remain limited. In this study, sampling and analysis methods, occurrence, source analysis and health risk of AMPs were summarized and discussed. According to the different sampling methods, AMPs can be divided into suspension microplastics (SAMPs) and deposition microplastics (DAMPs). Previous studies have shown that SAMPs and DAMPs differ in composition and abundance, with SAMPs generally having a higher fraction of fragments. The mechanism of the migration of AMPs between different media was not clear yet. We further collated global data on the composition characteristics of MPs in soil and fresh water, which showed that the fragment MPs in soil and fresh water was higher than that in the atmosphere. Polymers in soil and fresh water were mainly PP and PE, while AMPs in the atmosphere were mainly PET. The shape composition of the MPs in both atmospheric and freshwater systems suggests that there may be the same dominant factor. The transport of AMPs and source apportionment were the important issues of current research, but both of them were at the initial stage. Therefore, AMPs needs to be further studied, especially for the source and fate, which would be conducive to understand the global distribution of AMPs. Furthermore, a standardized manual on sampling and processing of AMPs was also necessary to facilitate the comparative analysis of data between different studies and the construction of global models.

Metallic Implants Used in Lumbar Interbody Fusion

Over the last decade, pedicle fixation systems have evolved and modifications in spinal fusion techniques have been developed to increase fusion rates and improve clinical outcomes after lumbar interbody fusion (LIF). Regarding materials used for screw and rod manufacturing, metals, especially titanium alloys, are the most popular resources. In the case of pedicle screws, that biomaterial can be also doped with hydroxyapatite, CaP, ECM, or tantalum. Other materials used for rod fabrication include cobalt-chromium alloys and nitinol (nickel-titanium alloy). In terms of mechanical properties, the ideal implant used in LIF should have high tensile and fatigue strength, Young's modulus similar to that of the bone, and should be 100% resistant to corrosion to avoid mechanical failures. On the other hand, a comprehensive understanding of cellular and molecular pathways is essential to identify preferable characteristics of implanted biomaterial to obtain fusion and avoid implant loosening. Implanted material elicits a biological response driven by immune cells at the site of insertion. These reactions are subdivided into innate (primary cellular response with no previous exposure) and adaptive (a specific type of reaction induced after earlier exposure to the antigen) and are responsible for wound healing, fusion, and also adverse reactions, i.e., hypersensitivity. The main purposes of this literature review are to summarize the physical and mechanical properties of metal alloys used for spinal instrumentation in LIF which include fatigue strength, Young's modulus, and corrosion resistance. Moreover, we also focused on describing biological response after their implantation into the human body. Our review paper is mainly focused on titanium, cobalt-chromium, nickel-titanium (nitinol), and stainless steel alloys.

From properties to toxicity: Comparing microplastics to other airborne microparticles

Microplastic (MP) debris is considered as a potentially hazardous material. It is omnipresent in our environment, and evidence that MP is also abundant in the atmosphere is increasing. Consequently, the inhalation of these particles is a significant exposure route to humans. Concerns about potential effects of airborne MP on human health are rising. However, currently, there are not enough studies on the putative toxicity of airborne MP to adequately assess its impact on human health. Therefore, we examined potential drivers of airborne MP toxicity. Physicochemical properties like size, shape, ζ-potential, adsorbed molecules and pathogens, and the MP's bio-persistence have been proposed as possible drivers of MP toxicity. Since their role in MP toxicity is largely unknown, we reviewed the literature on toxicologically well-studied non-plastic airborne microparticles (asbestos, silica, soot, wood, cotton, hay). We aimed to link the observed health effects and toxicology of these microparticles to the abovementioned properties. By comparing this information with studies on the effects of airborne MP, we analyzed possible mechanisms of airborne MP toxicity. Thus, we provide a basis for a mechanistic understanding of airborne MP toxicity. This may enable the assessment of risks associated with airborne MP pollution, facilitating effective policymaking and product design.

A rapid review and meta-regression analyses of the toxicological impacts of microplastic exposure in human cells

Humans are exposed to microplastics (MPs) daily via ingestion and inhalation. It is not known whether this results in adverse health effects and, if so, at what levels of exposure. Without epidemiological studies, human cell in vitro MP toxicological studies provide an alternative approach to this question. This review systematically synthesised all evidence and estimated thresholds of dose-response relationships. MEDLINE and Web of Science were searched from inception to March 2021 and study quality was rated using a novel risk of bias assessment tool. Seventeen studies were included in the rapid review and eight in the meta-regression. Four biological endpoints displayed MP-associated effects: cytotoxicity, immune response, oxidative stress, barrier attributes, and one did not (genotoxicity). Irregular shape was found to be the only MP characteristic predicting cell death, along with the duration of exposure and MP concentration (μg/mL). Cells showed varying cytotoxic sensitivity to MPs, with Caco-2 cells (human adenocarcinoma cell line) being the most susceptible. Minimum, environmentally-relevant, concentrations of 10 μg/mL (5-200 µm), had an adverse effect on cell viability, and 20 μg/mL (0.4 µm) on cytokine release. This work is the first to quantify thresholds of MPs effects on human cells in the context of risk assessment.